How Surfing Works


Surfing Image Gallery There are some specific requirements for good surf conditions, and these conditions exist only along the world's coastlines. See more surfing pictures.
Photo courtesy of Dreamstime

The basic idea behind ­surfing has been around for thousands of years. It probably star­ted when Polynesian fishermen discovered that catc­hing a wave was a speedy way to get to shore. In Hawaii, surfing gradually became a sport and an expression of social status -- the longer the surfboard, the more important the ­surfer's role in the community.

When missionaries and colonists arrived in Hawaii in the 1700s, surfing's reputation soured. Some newcomers were offended by the idea of scantily-dressed men and women surfing together. Missionaries banned the sport, and the islands' native population declined in the face of an influx of colonists. As a result, the practice of surfing dwindled until the 1900s, when surfers like George Fre­eth and Duke Kahanamoku caught the eye of the public and the media. This sparked resurgence in surfing as a recreational activity.

­As surfing grew in popularity, it changed dramatically. Hawaiian surfboards had been 10 to 16 feet (3 to 4.9 meters) long and made from solid wood. They could carry a person from the breakers to the shore, but they were heavy and hard to steer. Twentieth-century surfers made improvements to surfboards that allowed riders to control how and where they moved on the waves. New materials made boards lighter and easier to manage while fins and new board shapes added stability and maneuverability. Instead of simply aiming a board at the shore and trying to stay afloat, surfers could rapidly change direction, position themselves precisely on a crashing wave and even launch themselves from a wave's crest.

In his book "Roughing It," Mark Twain describes trying to surf -- and failing.
Public domain image

The ability to balance and maneuver on rapidly-moving water is pretty amazing, but it's not the only incredible thing about surfing. There are some specific requirements for good surf conditions, and these conditions exist only along the world's coastlines. Artificially constructing waves or changing the way natural waves break is difficult or even impossible -- in other words, you can only surf where the good waves are. In spite of this limitation, surfing has spawned a musical genre, multiple films, a wealth of slang terms and an entire culture.

One reason behind surfing's popularity is that it doesn't take a lot of gear to get started. We'll look at surfboards in the next section.

Surfboards

Long and shortboards
Long and shortboards

The biggest and most expensive requirement is a surfboard, which can cost anywhere from $150 to $500. These boards come in a range of basic shapes and sizes within two broad categories -- longboards and shortboards. Both types can have permanent or removable fins on their undersides, as well as strips of sturdy material known as stringers to help hold the board together. The sides of the surfboards, known as rails, can be rounded or tapered in a variety of ways to suit different surfers' preferences. The bottom of the board, or rocker, can curve to different degrees, changing how much of the board is in contact with the water.

Longboards are usually at least 9 feet (2.7 meters) long, and some are as long as 12 feet (3.7 meters). They are generally less maneuverable but more stable than shortboards. Shortboards are usually between 5 and 7 feet (1.5 and 2.1 meters) long, and they come in several shapes. As their names imply, fishes and eggs are short and wide. Funboards are a little longer and work well as all-purpose boards. Long, tapered shortboards known as guns are for expert surfers and exceptionally big surf.

Early Hawaiian surfers carved and shaped their own boards using local wood. Today's surfers can choose from custom-shaped boards or mass-produced boards known as pop-outs. Pop-outs get their name from the manufacturing process -- they pop out of factory molds. Both types are usually made of polystyrene or polyurethane foam covered in fiberglass and resin. In some people's minds, these artificial materials contradict the environmentally-friendly mindset of many surfers. An alternative is the Eco Board, developed by Project Eden. The Eco Board is made from balsa wood, hemp cloth and plant-derived resins.

Some surfers follow the examples of Hawaiian and early modern surfers by making their own boards. These boards start as blocks of foam or partially-shaped foam boards called blanks. After shaping the board, the surfer seals, or glasses the board with resin and fiberglass cloth. You can see a step-by-step video guide of what it takes to shape a surfboard at Surfline.

Surfing Gear

Surfing gear
Surfing gear

A surfboard allows a person to ride the waves, but several other pieces of equipment help protect riders from the water and the elements:

  • Wax adds a high-traction layer of bumps to the board's deck, or standing surface. Different waxes are most suited for different water temperatures. The wax layer helps the rider stay on the board, and it gradually smoothes out during use. Surfers can then add new wax or refresh the existing layer using a wax comb.
  • Board shorts are sturdier versions of swim trunks. With the increased popularity of women's surfing, manufacturers have developed board shorts that fit women.
  • Rash vests are fast-drying shirts that help prevent chafing, scrapes and injuries from impact with water. Many rash vests also offer protection from the sun by blocking UV radiation.
  • Wet suits help surfers stay warm in cold water.
  • A leash connects to a plug or cup on the board, helping to keep the surfer from losing the board while surfing.

Of course, surfing also requires a mode of transportation for getting to the beach. We'll look at what happens once the surfer gets to the water in the next section.

Learning to Surf

If you've ever learned to ride a bicycle, you might understand a little bit about what it takes to learn to surf. For most people, learning to ride a bike involves an awkward combination of pushing off, trying to balance and steering wildly before falling over. But eventually, you get it, and for most people who learn to ride a bike after a series of falls, that first moment of balancing on two wheels is incredible.

Surfing is similar. It requires balance and coordination, and getting started on a wave involves a key movement known as the pop-up. Like the push-off when riding a bike, the pop-up is central to riding a wave. Here's what happens:

  1. The surfer leaves from shore and paddles out into the surf while lying on the board.
  2. The surfer floats in the water near the spot where the wave will begin to break.
  3. When a wave approaches, the surfer paddles hard to catch up with it. This step, known as catching the wave, can be tricky, and it requires significant upper-body strength.
  4. Just before the wave starts to break, the surfer pushes down on the board as though he is doing a push-up. At the same time, he draws his legs up under his body, plants his feet and stands up.

From there, skilled surfers can perform all kinds of interesting maneuvers. They generally stay just ahead of the break, allowing the wave to propel them toward the beach. On large waves that break in the shape of a tube, surfers can duck into the barrel itself, disappearing from view in the watery tube. Surfers can move up and down on the wave's face, cut back toward the breaking water or allow their momentum to propel them off of the wave's surface. Since the surfboard is buoyant, surfers can land back on the wave and continue to ride it. Skilled surfers can position themselves on the front of the board, wrapping all ten of their toes around the board's nose. This is the origin of the term hang ten.

A surfing class

Getting upright and maneuvering on the wave's leading edge aren't the only parts of surfing that require balance and skill. Paddling out to the line-up, or the area of breakers where the surfers gather to catch a wave, requires balance and endurance. It also requires the surfer to understand how waves break so that he can decide the best path to take to the line-up. Paddling through the breaking water would be difficult, and it would lead to the risk of colliding with other surfers. For this reason, surfers paddle toward the lineup in a curve that bypasses the breaking water in favor of smoother waves.

In addition, when paddling through big waves, surfers must get out of the waves' way to keep from being pushed back toward shore. Surfers do this by going under water. A surfer on a longboard usually rolls underneath the board and pulls its nose underwater. This is a turtle roll. Surfers on shortboards, on the other hand, duck dive by pushing the nose of the board underwater and leaning into the wave. Either way, the bulk of the wave's face travels over the submerged surfer.

Surfing Physics

Everything about surfing, from the ability to stay afloat on the waves to the necessity of duck diving, comes from basic physics. Newton's laws of motion, which describe the movement of matter, contribute heavily to maneuvering and staying afloat. Newton's first law states that objects in motion, like waves, tend to stay in motion, while objects at rest, like a floating surfboard, tend to stay at rest. This is why a surfer has to paddle to catch a wave. According to Newton's third law, every action has an equal and opposite reaction. When a rider pushes down one edge of the board, that edge pushes into the water, which pushes back up against the board. As a result, the board starts to turn. You can see more about this process in How Personal Watercraft Work.

Here's a run-down of other physics principles that affect surfing:

  • Buoyancy: The surfboard's buoyancy, or ability to float, comes from its density. The board is less dense than the water underneath it. The board's coating is also waterproof, keeping water from seeping in, soaking the foam inside and pulling the board under.
  • Surface tension: The molecules that make up water are attracted to one another, so they create a surprisingly strong film at the water's surface. This film is one reason why a wave holds it shape, and it helps keep the surfboard afloat.
  • Gravity: While buoyancy keeps the surfboard afloat, gravity pulls it and its rider toward the water. Gravity's pull helps the rider hold his position on the moving, nearly-vertical face of a wave.
  • Mass and shape: The surfboard and its rider both have a center of gravity, which is related to their shape and mass. When riding the waves, the rider can move his center of gravity to shift the board's angle in the water. For example, moving toward the tail of the board will cause the nose to lift up from the water in response.
  • Hydrodynamic forces: Hydrodynamic forces are essentially the same as aerodynamic forces. These forces, like lift and drag, can dramatically affect how waves form and how the waves interact with the surfer's board.

Next, we'll examine the specifics of how waves form, especially the dramatic waves found in famous surfing spots.

The Physics of Waves

Part of the sport of surfing is the search for big, interesting waves that are fun to ride. These waves can be huge, like Mavericks off the coast of San Francisco, which can reach up to 50 feet (15 meters). Another famous surfing wave, the Banzai Pipeline, breaks over a reef off the coast of Oahu, Hawaii. It's one of many plunging waves that creates a pipe-like space, or barrel, that surfers can fit inside. Some of these waves are so big that swimmers can't swim out to them safely. Reaching these waves involves tow-in skiing, or traveling to the wave by being towed behind a personal watercraft.

No matter how big or interestingly-shaped popular surfing waves are, they all form because of two basic factors:

  • The interaction between wind and water
  • The interaction between water and land

A third influence is the tide. Lots of different factors contribute to the Earth's tides, but the pull of the moon's gravity on the Earth is the biggest. There are also other factors that can contribute to tsunamis and other rare types of waves, but wind, water and land do most of the work when it comes to the waves used for surfing.

To understand how they form, it's helpful to know a few basic facts about ocean waves. Waves are essentially energy moving through matter. If you looked at the cross-section of an idealized ocean wave, it would look like a transverse wave. The surface of the wave moves up and down, which is perpendicular to the left-to-right direction that the wave itself moves.

But ocean waves are a little more complicated than ordinary transverse waves. They're really orbital progressive waves. The water molecules that make up the wave move in circles, or orbits, as the wave progresses. You can visualize this movement by thinking of the particles near the wave's surface. If the wave is passing in front of you from left to right, the particles move in a circle in a clockwise direction. They move up the wave, across its crest and down into its trough.

The ocean's orbital waves get their start when wind blows on the open ocean. A gentle wind doesn't have much of an affect - it makes ripples in the water that spread the same way ripples do in a pond or a fish tank. But the stronger the wind becomes, the more it pushes against the water. It transfers energy to the water as it makes peaks and white caps in the water's surface. This region of white caps is chaotic, and the water can move choppily in random directions. The churning peaks give the wind more surface area to grab on to, which lets the wind force the water into even higher caps.

The height and shape of the white caps comes from three primary factors:

  • How long the wind blew over the water
  • How hard it blew
  • The surface area of the ocean that the wind affected, or the fetch

A very hard wind blowing for a long time over a large expanse of ocean will lead to large, frothy white caps. These eventually become large waves, which is why surf conditions are often good after a storm at sea. Satellite data used to track surface winds from outer space has helped forecasters predict where the surf will be high based on oceanic weather patterns.

Breaking Waves

As these peaks move away from the wind, they spend some of their energy through motion. This causes the peaks to smooth out into rounded swells. The swells collide with one another, and some of them combine through constructive interference. The larger, rounded swells begin to travel in approximately the same direction as the prevailing wind that originally created the whitecaps.

The swells become breaking waves when they reach shallower water. This can happen at the shoreline, at a point extending into the ocean or when the waves pass over an obstruction like a sandbar or a reef. Here's what happens when the wave gets to water that's about half the depth of its wavelength:

  • The swells slow down as the water beneath them gets shallower. As a result, the waves get closer together, much the way a line of cars will get closer together if the car in front starts to slow down.
  • The leading edge of the swell becomes increasingly vertical as it slows while the trailing edge continues to look like a rounded slope.
  • The waves get taller as the solid surface under them and the waves' energy pushes the water upwards.

Eventually, the wave crests, or breaks -- the fast-moving back of the wave spills over the slowing front of the wave. The exact shape of the ocean floor has a dramatic difference on how the waves break. If the shore slopes gently upward, the wave will gently spill over as it crests. A steep slope can cause waves that break suddenly and dramatically.

The cresting waves can travel for thousands of miles before reaching shore and becoming conducive to surfing. They have an enormous amount of power and momentum. For these and other reasons, they can become dangerous to even experienced surfers. Next, we'll look at surfing safety and the dangers inherent in the ocean.

Surfing Dangers

Rules of surfing
Rules of surfing

Tall, powerful waves that break cleanly are at the heart of surfing. However, the qualities that make these waves alluring can also make them dangerous. Waves start to break when they reach water that's about 1.3 times their height. In other words, even if the wave seems to be far from shore, the water under it isn't very deep. In addition, since many waves break over coral reefs, the surface under the water can be sharp and jagged. Surfers who wipe out, or fall off their boards, can potentially hit submerged obstacles or the hard surface under the water.

The water itself can become a hazard as well. The water that reaches the shore must return to the sea, and in the right conditions, this retreating water can form a rip current. A rip current is a fast-moving current moving toward the open sea. Swimmers who are caught in a rip current can be swept out further than they can swim back, or they can exhaust themselves fighting against the current. Most experts recommend swimming parallel to the shore to escape the pull of a rip current. See How Rip Currents Work to learn more.

As surf areas become more crowded, surfers also have the potential to collide with each other. This is one of the reasons why responsible surfers follow a code of etiquette that determines who has the right-of-way on a wave. Although these guidelines can vary from beach to beach, in general, the surfer closest to the wave's break has the right-of-way. If a surfer is already upright on a wave, he has priority over the other surfers.

Even if all of the surfers in an area are following guidelines for courteous riding, collisions are still possible. This is especially true if a surfer falls off of the board and loses it. In addition, surfers can collide with debris and trash floating in the water. This is one reason why surfers have started organizations like Surfers Against Sewage to fight for cleaner water.

Another common surfing hazard is the wildlife native to the ocean. Some people associate shark attacks with surfing, but these attacks are relatively rare. However, sharks do live near many popular surfing areas, and it's easy for a shark to mistake a paddling surfer for one of its food sources. Surfers can also encounter jellyfish, rays and other sea animals that can bite or sting.

Surfing Tips

Tips for surfing safely include being familiar with the beach before you start surfing.
Tips for surfing safely include being familiar with the beach before you start surfing.
Photo courtesy of Dreamstime

Here are some tips for surfing safely:

  • Apply sunscreen before getting into the water.
  • If you're surfing in cold water, wear a properly-fitting wetsuit - a wetsuit that's too big won't keep you warm. Surfing in cold water without a good wetsuit could lead to hypothermia, especially in the event of becoming stranded without a board.
  • Make sure your surfboard is undamaged and has a good, bumpy coat of wax on its deck before getting into the water.
  • Attach your board leash securely to the leg that is farthest back when you are on the board.
  • Never paddle farther out than you can swim back if you lose your board.
  • Never surf alone.
  • Check the surf forecast before leaving home and obey all posted surf and swim warnings.
  • If you're a beginner, practice popping up and surfing in areas that aren't crowded with surfers and swimmers. Consider taking a class from an experienced instructor.
  • Familiarize yourself with the surf and shore of the beach before you start surfing.

To learn more about surfing, waves and related topics, check out the links on the next page.

Related HowStuffWorks Articles

More Great Links

Sources

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  • California State University Monterey Bay. "News: Mavericks' Secret Revealed by Seafloor Mapping." http://news.csumb.edu/site/x18876.xml
  • California Surf Museum http://www.surfmuseum.org
  • DeMestre, Neville. "Mathematics and Bodysurfing." Australian Mathematical Society Gazette. September 2004 (5/21/2007). http://www.austms.org.au/Publ/Gazette/2004/Sep04/demestre.pdf
  • Eden Project. "Eco Surfboard." http://www.edenproject.com/foundation/2423.html
  • Exploratorium. "Hanging Ten." (5/21/2007). http://www.exploratorium.edu/theworld/surfing/index.html
  • ExtremeHorizon. "Surfboard Construction." http://www.extremehorizon.com/surfboard_design.asp
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